1. Field of the Invention
The present invention relates to a vehicle-steering control apparatus such as an electric power steering apparatus and an automatic steering apparatus.
2. Description of the Related Art
Heretofore, it has been common to increase power supply voltage in order to raise the efficiency of large-power vehicular equipment. Although power supply (battery) voltage in passenger cars, for example, has generally been set at 12V, power supply voltage in commercial cars such as trucks has been set at 24V as they need greater power supply. It has also been considered to set power supply voltage at 42V even in passenger cars as equipment mounted therein increases. Moreover, a power supply capable of supplying voltage as high as 200V or 300V is even mounted in electric cars.
There is a known electric power steering control apparatus to be mounted in a high-voltage car system as disclosed in IP-A-2000-168605, for example. Such an electric power steering control apparatus has been designed for optimum motor operation in accordance with the power supply voltage and motor load current conditions by providing switching elements for the high potential side of a bridge circuit comprising two sets of driving means including a first driving means 321 corresponding to a first power supply (e.g., 24V) and a second driving means 322 corresponding to a second power supply (e.g., 12V). See FIG. 8, for example.
However, the problem in the aforementioned prior art steering control apparatus is that the apparatus tends to become complicated, thus resulting in a cost increase, because the number of switching elements in the bridge circuit increases and a plurality of driving circuits for driving these switching elements are also required.
An object of the present invention made to solve the foregoing problems is to provide an efficient steering control apparatus fit for use in vehicles with high-voltage power supply at 200V, 42V and 24V without incurring complication of the apparatus in structure and a cost increase.
A steering control apparatus according to the invention comprises a first power supply, a second power supply for outputting a voltage lower than the voltage of the first power supply, a motor for generating an auxiliary steering power, control means for controlling the motor, and driving means for driving the motor in response to the output of the control means, wherein power is supplied from the first power supply to the driving means and that power is supplied from the second power supply to the control means.
A steering control apparatus, wherein the second power supply is made a DC-DC converter which is operated by supplying power from the first power supply.
A steering control apparatus comprises a power supply, a motor for generating an auxiliary steering power, control means for controlling the motor, and driving means for driving the motor in response to the output of the control means, wherein a switching regulator is provided for lowering the output voltage of the power supply, and the control means is supplied with power via the switching regulator and that the driving means is supplied with power via the power supply.
The control means, the driving means and the switching regulator are housed in one and the same case.
A series regulator is provided between the switching regulator and the control means.
The control and driving means are electrically grounded.
The control and driving means are electrically insulated.